Typically a marine vessel is steered via a steering mechanism that drives the ship's steering device, i.e. rudder. A rudder redirects the water past the stern, thereby imparting a turning or yawing motion to the vessel. In small boats, a tiller (i.e., a pole) is attached to the top of the rudder and is used by a helmsman to move the rudder and thereby to steer the boat. In large ships a steering wheel is linked to the rudder via cables, pushrods or hydraulic means. Manual steering of the vessels involves moving the tiller or steering wheel by a helmsman. Automatic steering (or autopilot) involves receiving input from one or more sensors, calculating the required steering movement and driving the steering device according to the calculated movement. Typical sensors include a compass, global position system (GPS) and Speed log (measuring speed of the vessel through the water), among others. An automatic steering system includes computing hardware and software and is used to maintain a chosen course or track line without constant human action.
Currently the majority of marine vessels are capable of being steered both manually and automatically. Manual steering (with the autopilot off) is usually performed by a helmsman at the steering wheel directly controlling the ship's rudder. As the vessel is steered manually by the helmsman, the rudder activity to accomplish maneuvers is usually excessive, even for a highly skilled helmsman. Automatic steering with current autopilot systems on often face the same challenges since present-day autopilots execute some, but not all of maneuvers required in a selected voyage plan. In particular, even with an autopilot system on, all maneuvers are initiated manually.
Accordingly, there is a need for an improved marine vessel autopilot system that reduces excessive rudder activity during steering and is capable of initiating and executing automatically all maneuvers required to complete a selected voyage plan.